Sharks will be smaller in size and poorer hunters by the end of the century due to warming oceans, marine ecologists say.

A report by the University of Adelaide's Environment Institute showed warmer waters and ocean acidification would slowly destroy the ability of sharks to hunt.

Researchers studied Port Jackson sharks in climate change conditions in large tanks with natural habitat and prey over seven months.

They found the sharks took a much longer time to find their food or, in some cases, did not bother trying.

The study's leader Associate Professor Ivan Nagelkerken said the combination of warmer water and high carbon dioxide levels increased the amount of food the sharks needed.

"We actually found that after long-term exposure these sharks grew much smaller because they couldn't find enough food to sustain their higher energetic demands," he said.

Professor Nagelkerken said the climate change conditions reduced the sharks ability to find food through smell.

"In warmer water sharks are hungrier but with increased CO2 they won't be able to find their food," he said.

But he said sharks would likely maintain their status on the food chain as other species would also shrink in size.

"The effect of ocean acidification on loss of hearing, vision and smell has been quite ubiquitous across a range of different animals, not only fish, it's also been shown in crabs, snails and other species."

Professor Nagelkerken said the impact of climate change could result in fewer shark attacks due to a reduction in hunting.

"We should keep in mind that humans aren't natural prey of sharks ... but if these species lose their sense of smell potentially that could lead to fewer attacks," he said.

But he said more research was needed to determine exactly what role a shark's sense of smell played in attacks.

"We don't know much about how sharks actually attack humans, if it's by accident, if they see them, or if they smell them from longer ranges," he said.

The report found the effects of climate change and ocean acidification could also accelerate the extinction rates of shark species, one third of which are already under threat due to overfishing.